The present disclosure relates to an electrostatic latent image developing toner including toner particles.
In a technical field relating to image formation (such as a copying machine), an electrostatic latent image developing toner is fixed on a recording medium (such as paper) through application of heat and pressure by using a fixing roller or the like. Regarding this fixing operation, there are demands for energy saving in the fixing operation and compactness of a fixing device. Therefore, a toner that can be satisfactorily fixed on a recording medium at a lower temperature than in the conventional technique is desired. Besides, in order to obtain a toner that can be satisfactorily fixed at a low temperature, a production method for a toner using a binder resin having a low melting point (or a binder resin having a low glass transition point), or a mold release agent having a low melting point has been proposed. When such a toner is stored at a high temperature, however, there arises a problem that toner particles included in the toner are easily aggregated. The charge amount of the aggregated toner particles is easily lowered as compared with the charge amount of toner particles not aggregated. Accordingly, in an image formed by fixing aggregated toner particles on a recording medium, an image defect occurs in some cases.
As a countermeasure, a toner including toner particles having a core-shell structure has been proposed for purpose of improving the fixability of a toner in a low temperature region (low-temperature fixability) and the storage stability of a toner at a high temperature (high-temperature preservability) and inhibiting the blocking property of a toner. In the toner particles having the core-shell structure, a toner core containing a binder resin having a low melting point is coated with a shell layer. A resin constituting the shell layer has a glass transition point higher than the glass transition point of the binder resin contained in the toner core.
As a toner particle having the core-shell structure, a toner particle in which the surface of a toner core is coated with a thin film containing a thermosetting resin has been proposed. This toner core has a softening temperature of 40° C. or more and 150° C. or less.